1. Field of the Invention
The invention relates to the field of aromatic and aliphatic isocyanates in which two isocyanate groups of markedly different reactivity are present.
2. Description of the Prior Art
Aromatic diisocyanates such as 2,4- and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate and mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and polyphenyl polymethylene polyisocyanates, aliphatic diisocyanates such as hexamethylene diisocyanate-1,6 and cycloaliphatic diisocyanates such as 3-isocyanatomethyl-3,3,5-trimethylcyclohexylisocyanate, are known commercial products which are preferably used in the preparation of polyurethane plastics. The polyisocyanates are commonly prepared from the corresponding amino compounds by phosgenation and subsequent thermal cleaving of the intermediate carbamic acid chlorides. Numerous organic mono- and polyisocyanates are described, for example, in the Annalen der Chemie 562 (1949), page 55, et seq.